A large commonmode voltage would be produced by the motor drive system of threephase inverter, which had great harm to the motor, and the influence of deadband was ignored by traditional pulse width modulation (PWM) commonmode voltage suppression. In order to effectively suppress the commonmode voltage of the threephase PWM inverter, an improved nonzero vector PWM method was proposed on the basis of the analysis of the traditional commonmode voltage suppression methods. The proposed method could eliminate the commonmode voltage spike output from the inverter after adding deadband time. The effectiveness of the proposed method was verified by simulation software.